The ornamental design for a lanterntank, as shown and described.
FIG. 1 is a front elevational view of the lantern tank showing our new design;
FIG. 2 is a rear elevational view;
FIG. 3 is the right side elevational view;
FIG. 4 is the left side elevational view of the lantern tank;
FIG. 5 is a top plan view;
FIG. 6 is a bottom plan view of the lantern tank; and,
FIG. 7 is a perspective view, taken from an upper right perspective, showing the relationships of the apertures of the tank. Note the angled pyramidal protrusion for the preheating nozzle. Also note the raised central area which acts to register and locate the upper lantern components.